THIS INVENTION relates to a domed building structure assembled from a plurality of individual panels. Domed building structures of this general type are disclosed, for example, in U.S. Pat. Nos. 4,285,174; 4,665,664; 4,686,801 and 5,170,599, and EP-0773331A, to which reference should be had.
More particularly, the invention relates to a domed building structure comprising a plurality of substantially concentric parts disposed one above the other and including a central upper apex part and one or more lower parts each forming a respective frustum adjoining the part immediately above, and wherein each said frustum is formed of a plurality of panels each extending from the upper inner edge of the frustum to the lower outer edge.
The design of such domed structures is subject to various constraints, in addition to the normal physical and engineering constraints. Thus, whilst it is generally highly desirable, from the point of view of ease of manufacture and hence cost, that the individual panels making up such a structure should be substantially planar, with straight edges, this normally implies, in the case of a structure comprising a succession of tiered frustums, of the kind referred to above, that the number of panels in each frustum must be the same, with the consequence that the panels in the lower frustums are excessively large or at least excessively elongate in the circumferential direction of the frustum and/or that the panels of the upper frustums are unnecessarily narrow, both of which circumstances give rise to increased costs, including increased assembly costs and handling and transportation costs. Thus the problem arising in the prefabricating, or panelling of large diameter dome structures of the kind referred to, where these are of timber construction, is the limited availability of standard cross-sectional dimension timber in long lengths. Also as the length of a panel increases so does the load and stress that has to be resisted by that panel, so that larger cross-section timer and/or plywood is required to make the panel. These difficulties place a practical and economical limitation on the size of those structures.
The construction proposed in U.S. Pat. No. 5,377,460 does to a certain extent meet this problem but does not go far enough. It is limited to reducing the number of panels in succeeding rings or frustum is to one half at a diameter that is decided geometrically based on the number of panels in the lower-most ring.
It is one of the objects of the present invention to provide an improved dome structure of the kind referred to.
According to the invention, there is provided a domed building structure comprising a plurality of substantially concentric parts disposed one above the other and including a central upper apex part and one or more lower parts each forming a respective frustum adjoining the part immediately above, and wherein each said frustum is formed of a plurality of straight-edged panels. each extending from the upper inner edge of the frustum to the lower outer edge, each junction between panel edges at each said upper inner edge of the or each frustum being coincident with a respective junction between panel edges at the adjoining edge of the frustum or central upper part immediately above, and at least one said frustum comprising both four-sided and triangular panels, with each triangular panel having an apex coincident with a junction between four-sided panels in the upper inner edge of the respective frustum, and having a base forming a respective part of the lower outer edge of the respective frustum, and wherein each said four sided panel is trapezoidal, with the shorter of its parallel edges lying in the lower, outer, edge of the frustum and the longer of its parallel edges lying in the upper, inner edge of the frustum.